Generally, washing machines are classified into a pulsator type washing machine, a drum of which is mounted in a vertical direction, and a drum type washing machine, the drum of which is mounted in a horizontal direction.
In the drum type washing machine, as the drum is mounted in the horizontal direction as described above, laundry received in the drum is washed by a lifting and dropping operation.
In the above-mentioned washing machine, however, even when a washing process is carried out to wash a small amount of laundry and even when a washing process is carried out to wash laundry having low contamination, a large amount of washing water is unnecessarily consumed. Furthermore, the washing process is carried out for the same period of time as a normal washing process, and therefore, the power consumption is also unnecessarily large.
Especially, it is more efficient to carry out a wetting process before the washing process is carried out since the washing performance is increased by the wetting process. However, the amount of the washing water consumed when the wetting process is carried out is very large. For this reason, the wetting process is omitted when the normal washing process is carried out, and therefore, the best washing performance is not accomplished.
In order to solve the above-mentioned problems, a washing machine having a steam generation unit for supplying steam into a drum during a washing process has been used.
Hereinafter, such a conventional washing machine having a steam generation unit will be described with reference to the accompanying drawings.
FIGS. 1 and 2 are a side sectional view and a front sectional view illustrating the inner structure of a washing machine having a steam generation unit, respectively.
The washing machine includes a machine case 110, a tub 120, a drum 130, a steam generation unit, a temperature sensor 150, a circulating pump 160, and a circulation channel 170.
The machine case 110 constitutes the external appearance of the drum type washing machine. At the front part of the machine case 110 is formed a laundry inlet hole 111.
A door 140 is mounted to the machine case 110 adjacent to the laundry inlet hole 111 for, opening and closing the laundry inlet hole 111. At the inner circumference of the laundry inlet hole 111 is mounted a rim part 112, which accomplishes sealing between the door 140 and the laundry inlet hole 111.
Also, a washing water supply pipe 113, which supplies washing water into the tub 120, is mounted in the machine case 110. On the pipe line of the washing water supply pipe 113 is mounted a detergent box 114.
The tub 120 is mounted in the machine case 110 in a supported state.
To the lower part of the tub 120 is connected a water drainage channel 121, through which washing water is drained.
Also, a washing water heater 122, which heats washing water supplied into the tub 120, is mounted in the lower part of the tub 120. The drum 130 is rotatably mounted in the tub 120, and is disposed such that the open side of the drum 130 is directed to the laundry inlet hole 111 of the machine case 110.
At the circumference of the drum 130 are formed a plurality of through-holes 131, through which washing water and steam supplied into the tub 120 are introduced into the drum 130.
The steam generation unit is mounted such that the steam generation unit can evaporate water using high-temperature hot air and supply steam generated from the water evaporation into the tub 120 and/or the drum 130. The steam generation unit includes a heating part 210 for generating high-temperature hot air to evaporate water, and a steam supply pipe 220, through which steam generated from the water evaporation by the heating part 210 flows.
Also, the steam generation unit further includes an injection nozzle 230 for injecting the steam flowing through the steam supply pipe 220 into the tub 120 and/or the drum 130.
Hereinafter, a steam washing operation will be described based on the detailed construction of the steam generation unit and a process of supplying water to the steam generation unit.
FIG. 3 is a flow chart illustrating the conventional steam washing operation.
After initial water supply is completed, a heating step to generate steam is carried out, and the generated steam is supplied into the drum such that the interior temperature of the drum is increased to a predetermined temperature level (S301).
While the heating step to generate steam is carried out as described above, the circulation pump and the drum motor are driven on/off such that laundry can be uniformly wetted and the detergent can be uniformly applied to the laundry.
While the steam generated by the heating operation is supplied into the drum a step of detecting water level in the tub is carried out, and a step of determining whether water resupply is necessary or not is carried out based on the result of the water level detection. If necessary, the water resupply step is carried out.
When the interior temperature of the drum has reached a target temperature level while the heating step and the washing water circulating step are carried out, the heater of the steam generation unit is turned off, and the washing operation is carried out for a predetermined period of time (S302).
After the above-described washing operation is completed, the used washing water is drained, and a spin-drying operation is carried out (S303). After that, the supply of water to the tub for rinsing the washed laundry is initiated (S304).
Subsequently, the water supply is carried out until the water level in the tub reaches a target water level. After the water supply to the tub is completed (S305), the water supply valve to the tub is turned off (S306).
And a rinsing operation is carried out by the operation of the drum (S307). When the rising operation is completed (S308), it is determined whether the rinsing operation has been carried out for predetermined number of times (S309).
In this way, the water supply for rinsing and the rinsing operation are carried out for the predetermined number of times to remove contaminants, such as residua of the detergent, from the laundry.
The above-described conventional steam washing control method enables the laundry to be washed using steam whereby the laundry is washed in a small amount of washing water.